Plastic edge type filter



Jan. 15, 1952 R. R. LAYTE 2,582,340

PLASTIC EDGE TYPE FILTER Filed March 25, 1948 2 SHEETS--SHEET 1 I 421T l i v INVENTOR. 4 ADAM/DH A? LAVTf BY v Kam D"- an; 15, 1952 R, LAYT 21,582,340

PLASTIC EDGE. TYPE FILTER Filed March 25, 1948 2 SHEETSSHEET 2 Tm g2 INVENTOR.

T a PAC??? A? LAY ATTOP/VA'VS Patented Jan. 15, 1952 2,582,340 I PLASTIC EDGE TYPE FILTER Ralph E. Layte, Westfield, N. J., assignor to Purolator Products, Inc., Newark, N. J., a corporation of Delaware Application March 25, 1948, Serial No. 17,054

2 Claims. (Cl.210169) 1 This invention relates to improvements in filters and in methods of making the same.

A principal object of this invention is to provide an edge type filter of plastic material that is self-supporting and does not require a supporting frame.

A further principal object of this invention is to provide novel apparatus and a novel method of making such filters.

A further object of the invention is to provide an inexpensive plastic filter unit of rigid construction capable of withstanding relatively high or low pressures and having a large area of definitely sized filtering interstices within small compass and requiring a minimum of plastic in relation to efiective filtering surface and with whticl the need for a supporting frame is elimina e Another object of the invention is to provide a novel process of producing such filters rapidly, eificiently and inexpensivel A filter unit embodying the invention consists of a slotted plastic cylinder or tube composed of a helix of plastic ribbon of minute thickness having its wide faces normal to the axis of the helix, and means to space the turns of the helix to provide filtering slots, the spacing means preferably consisting of projections of predetermined height extending from one face of the ribbon. Preferably, the ribbon is preformed with definite uniform curvature, whereby without any deforming or straining, it naturally assumes helical shape with its wide faces transverse to the axis of the helix and with the turns of the helix spaced apart to a known distance by the said projections. The turns of the ribbon are definitely spaced to provide a succession of apertures or slots which are of uniform predetermined gauge or filtering width, corresponding substantially to the height of the projections and which may be so extremely narrow as to make the filter unit efiective to remove from fluid passing through it all but the most minute particles. Due to the extreme thinness of the ribbon, the total area of the apertures or slots, i. e. the effective filtering area, forms a much larger proportion of the total area of the filter element than in previously known filters of rigid construction andthere fore fluid to be filtered may be passed through the filter unit at a relatively high rate.

Although the plastic ribbon is uniformly curved or shaped so that it may easily be shaped or wound on edge in the form of a helix without any deforming or straining and will invariably tend to maintain its helical shape except for a tendency to bend due to its thin section, the tendency of the coils to slide sideways eccentrically from its major axis and then tendency to open up as would a too light spring upon the application of an elongating force must be eliminated} Means are provided to effect this. g The manner of preforming the ribbon' is a modification of that described, for example, in Liddell Patent 2,042,537 granted June 2,1936, the necessary modifications existing because of the use of plastic material rather than 'of metal for the ribbon.

Masses, quantities of or crystals of plastic material such as vinylidene chloride resins, polyvinyl butyral resins, nylon resins, viny chloride acetate resins are used. These materials, in addition to the various thermosetting resins, may be used in the case of oil filters. Inthe cases where corrosion or dissolving by the filtrate is not of importance, e. g, air, the selection of the material would be governed by the air temperature. In the case of corrosive liquids, such as acids or alkalis, the materials chosen would be those having good resistance to these substances. Hence, it may be stated that the choice of material to be used in the fabrication of the filter medium would be dependent upon the use "for which it is intended and governed by the properties of these resinous materials. Masses, quantitles of or crystals of materials just listed are placed in a hopper, heated to temperatures in prescribed ranges and by means preferably of a feed screw the heated plastic is extruded or forced under pressure and under heat through an extrusion nozzle of desired cross sectional shape to produce plastic wire or ribbon having the desired round, rectangular or trapezoidal cross section.

The plastic wire is then passed between rollers shaped and formed substantially in the manner described in the said Liddell patent, forming a plastic edge type filter ribbon simular to the metallic filter ribbon of said Liddell patent. The rollers are heated, for example, by electric induction coils or by other ways to provide confined or directed heat in said rollers within prescribed temperature ranges to soften the thermoplastic materials and to polymerize the thermal setting resinous materials to a point just prior to final polymerization.

The ribbon is then in formed helices guided into a split ring type of sleeve for retaining the helices or turns in alignment and concentricity, and the adjacent coil edges are forced together by a roller or other appropriate means and by friction of the sleeve. The sleeve is appropriately heated as by electric induction or in other Ways within prescribed temperature ranges to polymerize the plastic material of the coils to their final stage (in the case of thermal setting resins) and to soften such coils so that the plastic materials (of whatever type used) can be permanently joined together at the contact points of the ribs or risers or one coil or helix and the back face of the adjoining coil or helix.

The shape of the plastic ribbon may be modified in formation to provide additional means for aligning the coils and maintaining their alignment in the finished product.

If desired, other ways of joining the coils can be provided. Likewise, if desired, the coilsneed not be joined so that they can be separated for cleaning purposes.

The filter structures provided by this invention are stronger, more economical to make and are resistan to he deleterious effects of acids, caustics, -.etc-, depend nt upon the resin or plastic-used.

Other objects, novel feature and advantages of the invention-will beapparent from the following specification and accompanying drawing wherein:

Fig. 1 is a vertical, partially schematic diagram, partially in section of apparatus for producing-edge type plastic :filter elements embodying the invention;

Fig. 1a is a. perspective view of amodifiedform of roller for shaping a modified form of ribbon;

Fig. 1b is a similar perspective View of another modified form of roller for shaping a further modified form of ribbon;

Fig. 1c is a section taken .along line lc-ic of Eiglb;

Fig. 2 "is an elevational view .of one form of filter element ;embodying the invention;

Fig. 3 is an enlarged bottom plan view of one .of the helices or coils forming th filter;

Fig. 4 is enlarged partial section taken along ;line-.4--4 of Fig. 2;

Fig. :5 is a 'view similar to that of Fig. .3 of a modified :form of coilhelix orturn;

"Fig. -6 is an enlarged partial section similar to that of Fig. 4 of :a filter element embodying coil helices or turns of Fig. 5;

Fig. .7 is an enlarged fragmentary perspective view of a portion of a filter element embodying the coil helices or turns of Fig. 5;

Fig. :8 is a bottom plan View of a further modifled :form of .coil helix or turn;

Fig. 9 is ,a fragmentary elevation partially in section of a filter element embodying coil helices 01" turns of Fig. 8;

Fig. 10 is an enlarged fragmentary perspective view of a portion of a filter element embodying coil helicesor turns of Fig. 8; and

Fig. 1-1 is a vertical section of one form of a filter unit in which filter elements of the invention maybe employed.

Referring now to the illustrated forms of the invention shown more specifically in Figs. 2-4 inclusive, the filter element comprises a slotted cylinder H3 formed from a substantially flat -plas tic ribbon H of minute thickness and which is provided on one face with spaced transverse ribs l2 all of which extend a similar distance outwardly from one of the faces of the ribbon, which distance is suited to the purposes for which the filter is to be used so that the resulting apertures, slits or slots 13 are definitely sized to permit the desired flow and to remove all particles of greater 4 dimension than the height of the said ribs from the fiuid being filtered. If desired, the ribbon H can have the tapering cross-section described in the Liddell patent and the ribs l2 could have corresponding shape.

In the case of filters for lubricating oil of an internal combustion engine, the ribs l2 preferably should be upwards of one thousandth of an inch in height and not more than three thousandths, in order to remove the harmful abrasives and still allow the substantially clean oil to flow through the filter unit at such rate that the filter will be of practical utility. In other instances the range of heights of theribs may lie between .0005 inch to .030inc'n.

The dimensions of the ribbon are such as to provide a cylinder having strength to withstand the pressure and the service to which it is to be subjected.

The practical difiiculties of preparing the filter unit Hi from ribbon H are avoided by forming a very thin ribbon but preshaping it with definite uniform curvature so that it naturally tends to assume helical shape with its faces in contact and transverse to theaxis of the helix.

Furthermore, a cylindrical filter unit having the large ratio of effective filtering area to total area of filtering element contemplated by this invention would be at least one hundred times larger in diameter than the thickness of the ribbon (in direction parallel to the axis of the cylinder). .In such arrangement, the ribbon, if bonded at the ribs I2, has sufficient rigidity to hold the successive turns of the helix in alignment without the aid of auxiliary aligning or supportingmeans.

In an alternative form of element Illa as shown in Figs. 5 to 7 inclusive, the plastic ribbon Ila, is utilized for forming the filter element 18a. This ribbon Ha may be provided in addition to the ribs 12a with inwardly projecting lugs E la arranged at approximately spaced apart points of the internal edge of the ribbon Ha, or, if desired, arranged to project externally (not shown) of the outer edge of the ribbon I la. Each of these lugs I la is provided with a hole l5a. In this embodiment the tapered cross section of the ribbonis shown in Fig. '7. Such tapering is optional, however.

When ribbon Ila is formed into helices which are arranged in contact with each other With the ribs l2a abutting the unribbed adjacent surfaces of adjacent helices, lugs 54a and the bores [5a of various adjacent helices or turns are arranged to lie axially aligned so that rigid supporting rods lBa may be inserted and temporarily or permanently retained in the aligned bores 15a both during and subsequent to the permanent junction of the ribs [2a to adjacent surfaces of the adjacent helices. With such construction, the spacing 13a, provided between adjacent helices is arranged to be substantially the same as that of spaces 13 between the helices of the first described modification of Figs. 3 to 4 inclusive.

In another embodiment shown in Figs. 8 to 10 inclusive, the filter element 10b consists of the plastic ribbon llb. That ribbon lib in addition to having the ribs lf-lb, is further modified by providing lateral inwardly or lateral outwardly extending lugs I8 that are shaped at their ends 18b to provide shoulders l9 as seen in Fig. 10. The tapered cross section of the ribbon is optional. With the construction of this figure, when the helices are pressed together to form the filter element lob, the inner edges of adjacent helices or turns engage respective shoulders I!) of projections l8b provided on the preceding helices to prevent lateral displacement of the said helices. Such arrangement materially increases the strength of such filter elements lb. The spacing lab between adjacent helices is substantially the same as that 23 between the helices of the first modification of Figs. 2-4.

Plastic filter elements embodying the invention may be used in various types of filter structures. For example, in the structure shown in Fig. 11, the hollow casing 30 is provided with a casing head 3i. A sealing gasket 32 provides an effective seal at the joint between the head 3l and the casing 30. An inlet passage 33 serves to admit oil or other fluid to be filtered to the casing 30 and outlet passage 34 permits the illtered liquid to flow out of the casing. A plastic filter element l5, Illa or lilb is secured in place in. the axial direction of casing 30, for example, by an axially extending mounted bolt or member 35 which is headed at one end to engage a cap 3'! and threaded at 38 to screw into the head 3|. The cap 3? fits over one end or the filter unit l0, Illa, or lllb and the other end of the latter abuts the head 3| about a portion of the outlet 34. The oil or other liquid to be filtered flows to casing 3 through inlet 33, downwardly in the casing, laterally through the interstices l 3, I311 or l3b of the filtering element It, Illa or lb and upwardly to the outward flow passageway 34 as denoted by the arrows in Fig. 11. The flow direction may be reversed. Dirt is collected on the outer or inner surface of the supported filtered element ll) or llia or lb depending upon flow direction. The united head 3i and casing 3!! bearing the filter element l0, or llla or lb are supported by a retaining yoke 40 which serves to hold the head and casing in joined condition. These parts may be readily separated for inspection and cleansing or replacement of the filtering unit.

The method of forming the filtering elements comprising the invention is shown schematically in Fig. 1. Therein a container or hopper B is provided with a heating jacket 5| through which by way of inlet 52 and outlet 53 an appropriate heating medium may be circulated to provide temperatures in the range of 200 F. to 500 F. depending upon the resin used. If vinylidene chloride resin (Saran) is used the temperature range is 250 F. to 400 F. This heating medium may be steam or hot gaseous products of combustion or any other desirable medium. The hopper 5 is narrowed in a portion 54 and the portion 5 3 terminates in an extrusion nozzle 55. The extrusion nozzle 55 has desired cross-sectional shape so that any material extruded therefrom will have the same desired cross-sectional shape.

A feed screw 56 whose drive shaft 57 is appropriately driven operates in the narrow portion 54 of the hopper 50. This screw 56 acts to feed the contents or the hopper 50 to the extrusion nozzle 55 and to extrude such contents therefrom. Other extrusion means may be employed. The material inserted into the hopper 50 comprises masses, quantities or crystals of the plastic material hereinbefore described which soften and unify in the hopper under the heat provided by the medium in the jacket 5 I.

This softened material is fed by the feed screw 56 and extruded through the nozzle 55 as a continuous plastic wire. This Wire is fed directly from the nozzle and passes between a pair of cooperating. conical rollers 60 and GI. One of these rollers is provided with recesses 62 for forming the spacing projections or transverse ribs l2, l2a or lZb. The passage of the Wire between these rollers 60 and 6| which are appropriately heated as by electric induction coils 64 and 65 or in other suitable ways to temperatures ranging from 200 F. to 250 F. cfor vinylidene chloride resin and F. to 500 F. for other resins mentioned, acts not only to convert the extruded material into a thin fiat ribbed ribbon, but, also, gives to it definite predetermined curvilinear shape which causes the formed ribbon to tend to assume the form of a helix as shown in Fig. 3, 5 or 8 with its wide faces in abutting relationship. Preferably the formed ribbon II, I la or llb is guided to a split ring type of sleeve 65 and is moved into the latter by the aid of a guiding roller 61. The friction of the ribbon ll, Hot or lib against the internal surfaces of. the split ring 66 and the action of the'guiding roller 61 tends to compress the helices to bring the ribs l2, Hot or l2b of each into abutment with the adjacent unribbed surface of the adjacent helices.

The heat provided by the induction coil 64 and 65 to the rollers 50 and BI is sufiicient to polymerize the plastic material of the ribbon to the point just prior to its final polymerization point or stage. The sleeve 65 is heated either by an induction coil C or in other appropriate ways 'sufficiently to a temperature ranging from 250 F. to 300 F. for vinylidene chloride resin and 125 F. to 500 F. for other resins mentioned to provide polymerization heat for the material of the helices to polymerize it to its final stage and is, also, sufficiently high to soften the material enough to provide adhesion between abutting ribs and helix surface portions and thereby to effect a permanent joint at the contact points of the ribs on one coil with the back faces of the adjacent coils. If desired, the heating of the sleeve 56 can be made insufficient to effect permanent bonding and instead an appropriate adhesive can be applied to ribs [2, Ha or I2b prior to the entry into the sleeve 66 of the helices bearing such ribs. The heat of the sleeve in such event is made sufficient to polymerize the material of the helices to final stage and also to set the adhesive and thereby provide a permanent bond between the ribs and the back faces of the adjacent coil. The temperature range in such event of the sleeve is rirom 200 F. to 250 F. for vinylidene chloride resin and 125 F. to 500 F. for others of the resins mentioned.

In the event that it is desired to form filter elements of the forms described in Figs. 5 to 7 or 8 to 10 inclusive, the only replacement necessary is of the roller 6| so that the extruded ribbon passing either between a modified roller Bla (Fig. 1a) or a modified roller Gib (Figs. 1b and 1c) and a roller corresponding to a roller 60 will impart or provide the appropriate projections Ma or l8, lb and IS in addition to the ribs l2a or lZb. For example, to provide ribbon of the form shown in Figs. 5-'?, various of the depressions 62a of the roller Bla are provided with a lateral recessed bore portion 62b having an island 62c shaped to correspond to the lateral extensions Ma and position of hole l5a so that passage of the extruded material between a roller 60 and a roller Gla will form the lateral projection Ma with holes l5a in addition to the ribs l2a on ribbon Ila.

7 Similarly, if the ribbon [lb of the third modification is desired, a roller 61b (Figs. 1b and instead of roller BI is provided with recesses 62d to form the ribs 121) and in addition. these recesses 62d have additional depressions 63b necessary for the direct formation of the portions 18, 18b and the shoulders 19 of the ribs [2b. Substitution either of roller 6la or roller 61b as the case may be for the roller 9| is all that is required to produce the respective ribbons Ha or lib, instead of ribbon II.

By the term helix as used in the foregoing description and in the appended claims, it is intended to include elements which are substantially cylindrical in form, such for example, as truncated cones and similar shapes.

The structure above described combines the qualities of uniformly fine edge filtration, great structural strength and a high degree of filtering efiiciency, that is, a high ratio of effective filtering area to the total area of the filtering unit. The strength and uniformity of filtering qualities of tube filters are herein combined with the high filtering efficiency of a wire screen. The edgewise arrangement of the ribbon on the support combined with the lateral support given to each turn by the adjacent turn through the spaced ribs results in a very strong and rigid construction capable of withstanding pressures entirely outside the range of possibility of wire screens of corresponding filtering fineness and yet having a filtering efficiency comparable with that of wire screens. The efficiency of edge filters is combined with structural strength sufiicient to withstand high pressures in an inexpensive and light device which is economical to manufacture and of extreme durability.

While many modifications in form and arrangement may be made without departing from the spirit of the invention, it is apparent that the above described plastic filtering units combine the well known advantages of edge filtration with absolutely uniform predetermined width of the filtering apertures or slots so that rigid construction is effected and the aggregate area of the apertures or slots is large in relation to the total area of the unit and a very great saving in material is effected over other metal filters in relation to the filtering capacity provided.

While specific embodiments of the invention have been described, it will be understood that variations in details and in forms of construction and of details of method within the scope of the claims are contemplated. There is no intention, therefore, of limitation to the exact details shown and described.

What is claimed is:

1. In combination with a casing having an inlet and an outlet, a completely self-supporting filter unit comprising a helix composed of a thin narrow ribbon of plastic material with its width substantially normal to the axis of the helix, spacing ribs extending transversely of the ribbon on a wider face thereof, and aligning lugs integral with said ribs and projecting beyond a thinner face of the ribbon and substantially normal to the said wider face to define shoulders engaging a thinner face of an adjacent helical turn of said ribbon thereby aligning said turns.

2. The device of claim 1 in which the spacing ribs of the ribbon in each turn are permanently bonded to the adjoining face of the adjacent turn.

RALPH R. LAYTE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,744,510 Hele-Shaw et al. June 21, 1930 1,932,821 Henkel Oct. 31, 1933 1,974,235 Cammen Sept. 18, 1934 2,000,490 Mandahl May 7, 1935 2,042,537 Liddell June 2, 1936 2,188,643 Laderer Jan. 30, 1940 2,257,944 Fischbein Oct. 7, 1941 2,284,787 Winkler June 2, 1942 2,324,838 Harz et al July 20, 1943 2,330,282 Hazeltine et al. Sept. 28, 1943 2,360,570 Mattoon Oct. 17, 1944 2,375,246 Kasten May 8, 1945 2,489,292 Hobbs Nov. 29, 1949 FOREIGN PATENTS Number Country Date 9,228 Great Britain of 1911 308,573 Great Britain Nov. 14, 1929 486,186 Great Britain May 31, 1938 

